In the field of geophysical prospecting, the knowledge of the earth's subsurface structure is useful for finding and extracting valuable mineral resources such as oil and natural gas. A well-known tool of geophysical prospecting is a “seismic survey.” In a seismic survey, acoustic waves produced by one or more sources are transmitted into the earth as an acoustic signal. When the acoustic signal encounters an interface between two subsurface strata having different acoustic impedances, a portion of the acoustic signal is reflected back to the earth's surface. Sensors detect these reflected portions of the acoustic signal, and the sensors' outputs are recorded as data. Seismic data processing techniques are then applied to the collected data to estimate the subsurface structure. Such surveys can be performed on land or in water.
In a typical marine seismic survey, multiple streamer cables and one or more seismic sources are towed behind a vessel. A typical streamer includes multiple seismic sensors positioned at spaced intervals along its length. The seismic sensors often include pressure sensors (“hydrophones”) and accelerometers. The use of different sensor types enables better rejection of noise and directional filtering of seismic waves.
Suitable accelerometer types for use in marine seismic streamers include micro electromechanical systems (“MEMS”) accelerometers. Such accelerometers generally employ a semiconductor substrate with an etched or deposited mechanical element that moves or deforms in response to the sensor's acceleration. Circuitry on the substrate measures the degree of movement or deformation to generate a sensor output signal. Feedback can be employed to ensure that the sensor makes accurate measurements.
It should be understood that the drawings and detailed description do not limit the disclosure, but on the contrary, they provide the foundation for understanding all modifications, equivalents, and alternatives falling within the scope of the appended claims.